US5491248A - Readily dispersible bentonite - Google Patents
Readily dispersible bentonite Download PDFInfo
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- US5491248A US5491248A US08/425,534 US42553495A US5491248A US 5491248 A US5491248 A US 5491248A US 42553495 A US42553495 A US 42553495A US 5491248 A US5491248 A US 5491248A
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- bentonite
- water
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- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 title claims abstract description 112
- 229910000278 bentonite Inorganic materials 0.000 title claims abstract description 107
- 239000000440 bentonite Substances 0.000 title claims abstract description 107
- 229910000077 silane Inorganic materials 0.000 claims abstract description 20
- -1 silane compound Chemical class 0.000 claims abstract description 17
- 125000004432 carbon atom Chemical group C* 0.000 claims abstract description 5
- 125000001301 ethoxy group Chemical group [H]C([H])([H])C([H])([H])O* 0.000 claims abstract description 5
- 125000005843 halogen group Chemical group 0.000 claims abstract description 5
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 claims abstract description 5
- 125000000217 alkyl group Chemical group 0.000 claims abstract description 4
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 claims description 8
- IJOOHPMOJXWVHK-UHFFFAOYSA-N chlorotrimethylsilane Chemical compound C[Si](C)(C)Cl IJOOHPMOJXWVHK-UHFFFAOYSA-N 0.000 claims description 4
- YGUFXEJWPRRAEK-UHFFFAOYSA-N dodecyl(triethoxy)silane Chemical compound CCCCCCCCCCCC[Si](OCC)(OCC)OCC YGUFXEJWPRRAEK-UHFFFAOYSA-N 0.000 claims description 2
- CZWLNMOIEMTDJY-UHFFFAOYSA-N hexyl(trimethoxy)silane Chemical compound CCCCCC[Si](OC)(OC)OC CZWLNMOIEMTDJY-UHFFFAOYSA-N 0.000 claims description 2
- POPACFLNWGUDSR-UHFFFAOYSA-N methoxy(trimethyl)silane Chemical compound CO[Si](C)(C)C POPACFLNWGUDSR-UHFFFAOYSA-N 0.000 claims description 2
- FZMJEGJVKFTGMU-UHFFFAOYSA-N triethoxy(octadecyl)silane Chemical compound CCCCCCCCCCCCCCCCCC[Si](OCC)(OCC)OCC FZMJEGJVKFTGMU-UHFFFAOYSA-N 0.000 claims description 2
- 239000005051 trimethylchlorosilane Substances 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 70
- 239000002245 particle Substances 0.000 abstract description 27
- 239000000843 powder Substances 0.000 abstract description 16
- 230000015572 biosynthetic process Effects 0.000 abstract description 15
- 239000006185 dispersion Substances 0.000 abstract description 8
- 230000001747 exhibiting effect Effects 0.000 abstract 1
- 238000003756 stirring Methods 0.000 description 18
- 108010025899 gelatin film Proteins 0.000 description 7
- 230000000087 stabilizing effect Effects 0.000 description 6
- 238000005553 drilling Methods 0.000 description 5
- 230000002209 hydrophobic effect Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 150000004756 silanes Chemical class 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 4
- 239000004927 clay Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 229920003023 plastic Polymers 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 229910001415 sodium ion Inorganic materials 0.000 description 3
- 239000002689 soil Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 125000005103 alkyl silyl group Chemical group 0.000 description 2
- 239000002734 clay mineral Substances 0.000 description 2
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052901 montmorillonite Inorganic materials 0.000 description 2
- 239000003208 petroleum Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 125000005372 silanol group Chemical group 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005695 dehalogenation reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 230000005660 hydrophilic surface Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052909 inorganic silicate Inorganic materials 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 229910052622 kaolinite Inorganic materials 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- ARYZCSRUUPFYMY-UHFFFAOYSA-N methoxysilane Chemical compound CO[SiH3] ARYZCSRUUPFYMY-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000011085 pressure filtration Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 229910052903 pyrophyllite Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000000518 rheometry Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 230000035943 smell Effects 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
- C07F7/02—Silicon compounds
- C07F7/08—Compounds having one or more C—Si linkages
- C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
- C07F7/1804—Compounds having Si-O-C linkages
Definitions
- This invention relates to readily dispersible bentonite which can rapidly be dispersed in water while retaining viscosity and water impermeability inherent to bentonite.
- Bentonite is supplied on the market in a powdered form having a particle size of not greater than 150 ⁇ m, which is prepared by coarsely crushing ore from a bentonite mine, which contains about 10 to 40 wt % of water, to a size of about 10 mm or less, drying it in a rotary drier to reduce the water content to about 6 to 10 wt %, and pulverizing it in a roller mill or a hammer mill to the above size.
- a soil stabilizing fluid used in civil engineering works such as underground continuous wall construction or in-situ piling, and a drilling fluid (mud) used in development of underground resource energy, for example, drilling of an oil well, a geothermal well or a spring well, is generally prepared by dispersing powdered bentonite in fresh water in a concentration of 4 to 8 wt % by stirring it in a stirring machine and, if desired, adding adequate amounts of chemical substances, such as sodium carboxymethyl cellulose, polymers and surface active agents, in order to prevent deterioration due to contamination with cement or a brine such as seawater.
- chemical substances such as sodium carboxymethyl cellulose, polymers and surface active agents
- Bentonite is an alkaline clay mainly comprising a clay mineral montmorillonite and, unlike other clay minerals such as kaolinite or pyrophyllite, has a great cation-exchange capacity of 40 to 120 milliequivalents per 100 g of clay.
- the exchangeable cations include a sodium ion, a calcium ion, and a magnesium ion.
- bentonite having an abundance of sodium ions has such high hydrophilic properties that it absorbs a large quantity of water to increase its own volume remarkably, that is, it exhibits high swellability in water and is finally dispersed to colloidal particles and therefore has been used as a fundamental element of a stabilizing slurry or mud for drilling or boring works.
- Essential functions required for the material of stabilizing slurries or mud are proper viscosity and water impermeability.
- an object of the present invention is to provide readily dispersible bentonite which can be rapidly dispersed in water while minimizing formation of lumps without substantial reduction in viscosity and water impermeability inherent to bentonite.
- the present invention relates to readily (water) dispersible bentonite obtained by surface treating bentonite by with adding at least one alkyl-substituted silane compound represented by formula (I);
- R represents an alkyl group having 1 to 18 carbon atoms
- X represents a methoxy group, an ethoxy group or a halogen atom
- a and b each represents 1, 2 or 3, provided that (a+b) is 4; in an amount of not more than 1% by weight based on the bentonite.
- Bentonite powder comprises solid bentonite particles with a water content adsorbed on the surface thereof and air filling the gaps among the particles, and the particles agglomerate to form porous clay particles.
- the clay particles have a highly hydrophilic and highly polar surface and therefore tend to gather.
- the individual bentonite particles do not come into contact with water but gather to form clusters with a large amount of air entrapped therein, and only the outermost part of the clusters is first to be brought into contact with water.
- the bentonite contains abundant sodium ions, the surface of the bentonite cluster absorbs water owing to its strong hydrophilic properties and immediately smells with water to form a continuous water-impermeable gel film.
- the gel film is water impermeable and also adhesive, the air entrapped in the inside of the cluster cannot easily be displaced with outside water. It follows that the bentonite clusters rise to the water surface as lumps in the initial stage of stirring. If the lumps come into contact with each other in a turbulent flow by stirring, they tend to grow into larger lumps. In this stage, the lumps consist of white powder with its inside remaining dry. In the meantime, displacement of inside air with outside water through the gel film proceeds with time, and the water having entered through the gel film swells inside bentonite particles to gradually increase the transparency. At the same time, the lumps are disintegrated from their outermost part and become thinner. Finally, all lumps disappear to provide a uniform dispersion.
- Such a hydrophobic substance as meets the object should satisfy the following conditions; (1) to have no adverse influence on the viscosity and water impermeability of bentonite, (2) to produce a desired effect upon addition of a small amount, (3) to be moderately priced so that the increase in production cost of bentonite may be within an acceptable range, and (4) to be applied to the surface of bentonite particles by a simple and easy method.
- the means established by the present inventors is as follows. Coarsely crushed and dried ore of bentonite obtained by a conventional process for bentonite production is pulverized while sprinkling a proper amount of at least one of the following alkyl-substituted silane compounds, or powdered bentonite is mixed with a proper amount of at least one of the alkyl-substituted silane compounds which is added through sprinkling over the powdered bentonite, the compound thereby adhering as a hydrophobic substance on the surface of bentonite particles.
- alkyl-substituted silane compounds which can be used in the present invention are represented by formula (I):
- R represents an alkyl group having 1 to 18 carbon atoms (more preferably 1 to 6 carbon atoms);
- X represents a methoxy group, an ethoxy group or a halogen atom;
- a and b each represent 1, 2 or 3; and (a+b) is 4.
- alkyl-substituted silane compounds include methyltrimethoxysilane [CH 3 Si(OCH 3 ) 3 ], trimethylchlorosilane [(CH 3 ) 3 SiCl], trimethylmethoxysilane [(CH 3 ) 3 SiOCH 3 ], hexyltrimethoxysilane [C 6 H 13 Si(OCH 3 ) 3 ], dodecyltriethoxysilane [(CH 12 H 25 Si(OC 2 H 5 ) 3 ], and octadecyltriethoxysilane [C 18 H 37 Si(OC 2 H 5 ) 3 ].
- the optimum range for a combination of specific bentonite species and a specific alkyl-substituted silane compound can be decided by preliminary experimentation for evaluating the inhibitory effect on lump formation as well as the viscosity and water impermeability of the resulting dispersion.
- the amount to be added for producing a noticeable effect is from 0 to 1% by weight, preferably from 0.05 to 0.5% by weight, based on bentonite.
- the water content of the bentonite to which the alkyl-substituted silane compound is added may be in the same range as that of commonly available bentonite products, i.e., in the range of from about 6 to 10% by weight.
- the alkyl-substituted silane compound added to bentonite powder in an amount of not more than 1% by weight renders a part of the surface of bentonite particles hydrophobic owing to its remarkable water-repelling action attributed to the alkylsilyl group thereof.
- the surface of the bentonite particles is moderately prevented from absorbing water to form a continuous water-impermeable gel film. It follows that the clusters of bentonite particles achieve rapid displacement of the internal air with the outside water while minimizing formation and growth of lumps, and the clusters are crumbled and dispersed in water at a considerably increased speed by the turbulent flow of stirring.
- the alkyl-substituted silane compound used in the present invention is hydrolyzed on contact with water, thereby releasing the methoxy or ethoxy group by dealcoholization, or halogen atom by dehalogenation and, at the same time, providing a hydroxyl group on the silicon atom (to form a silanol group). Since the resulting silanol group is hydrophilic, it is adhered to the hydrophilic surface of the water-containing bentonite particles.
- U.S. Pat. No. 5,292,908 discloses modified bentonite which is dispersed in water to perform a function of adjusting rheology of an aqueous fluid, which is obtained by adding an alkyltrialkoxysilane to bentonite in such an amount that the resulting bentonite may not lose the water dispersibility, usually in an amount of 1 to 10 parts by weight per 100 parts by weight of bentonite, followed by treating in a water-free atmosphere to add an alkylsilico group to a part of the surface of bentonite particles.
- This technique is quite different from the present invention; the modified bentonite of U.S. Pat. No.
- 5,292,908 has an alkylsilico group permanently added to the surface thereof through a covalent bond that is formed by condensation (dealcoholation) between a hydroxyl group on the edge of montmorillonite crystal grains and the alkyltrialkoxysilane. Therefore, the treatment is accomplished under a water-free condition.
- the alkyl-substituted silane compound merely has to be physically adhered to the surface of water-containing bentonite particles so that the surface of the bentonite particles may temporarily exhibit hydrophobic properties to prevent formation of lumps immediately after the bentonite particles are poured into water and in the initial stage of stirring.
- the silane compound does not need to be permanently bound to the surface of bentonite particles through a chemical bond, and the amount of the silane compound to be added may be lower than the lower limit required for the above-described modified bentonite.
- the viscosity and water impermeability inherently possessed by bentonite are substantially guaranteed in the presence of such an alkyl-substituted silane compound.
- Treated Bentonite I was compared with the non-treated bentonite in inhibitory effect on lump formation as follows.
- Bentonite was treated with various alkyl-substituted silane compounds shown in Table 4 in the same manner as in Example 1 to prepare Treated Bentonite II to VI.
- Treated bentonite II to VI were evaluated by a dispersion test in the same manner as in Example 1. The results obtained are shown in Table 4. It is seen that the treated bentonite according to the present invention exhibits excellent dispersibility while retaining viscosity and water impermeability.
- the small lumps of powder having lost buoyancy are sufficiently moved in water by a stirring turbulent flow and rapidly become thinner and uniformly dispersed.
- the readily dispersible bentonite according to the present invention retains the viscosity and water impermeability essential to bentonite and therefore makes it possible to remarkably reduce the time and energy for dispersing bentonite in the preparation of a soil stabilizing slurry or mud for use in ground drilling works.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
Abstract
Readily dispersible bentonite comprising bentonite particles having adsorbed an alkyl-substituted silane compound represented by formula (I) onto the surface thereof is disclosed:
R.sub.a SiX.sub.b (I)
wherein R represents an alkyl group having 1 to 18 carbon atoms; X represents a methoxy group, an ethoxy group or a halogen atom; a and b each represents 1, 2 or 3, provided that (a+b) is 4; in an amount of not more than 1% by weight based on the bentonite. When poured into water and stirred, the treated bentonite is rapidly dispersed while minimizing formation of hardly dispersible lumps of powder to provide an aqueous bentonite dispersion exhibiting satisfactory viscosity and water impermeability.
Description
This invention relates to readily dispersible bentonite which can rapidly be dispersed in water while retaining viscosity and water impermeability inherent to bentonite.
Bentonite is supplied on the market in a powdered form having a particle size of not greater than 150 μm, which is prepared by coarsely crushing ore from a bentonite mine, which contains about 10 to 40 wt % of water, to a size of about 10 mm or less, drying it in a rotary drier to reduce the water content to about 6 to 10 wt %, and pulverizing it in a roller mill or a hammer mill to the above size.
A soil stabilizing fluid used in civil engineering works, such as underground continuous wall construction or in-situ piling, and a drilling fluid (mud) used in development of underground resource energy, for example, drilling of an oil well, a geothermal well or a spring well, is generally prepared by dispersing powdered bentonite in fresh water in a concentration of 4 to 8 wt % by stirring it in a stirring machine and, if desired, adding adequate amounts of chemical substances, such as sodium carboxymethyl cellulose, polymers and surface active agents, in order to prevent deterioration due to contamination with cement or a brine such as seawater. On being poured into water, powdered bentonite first forms lumps, which are then disintegrated by stirring it a long time into a uniform dispersion. In what follows, the single term "lumps" means undissolved lumps of powder which are formed when the powder is poured into water. Therefore, preparation of a soil stabilizing slurry or mud has required great energy and time for stirring. The higher the viscosity and water impermeability of bentonite due to the higher bonding force with water, that is, the higher the quality of bentonite, the greater the tendency to formation of lumps of powder which are hard to disperse in water.
As the depth reached by recent ground drilling works has increased, the demand for a stabilizing slurry or mud having high water impermeability sufficient to withstand high underground water pressure has been increasing. While bentonite of high quality meeting that demand has been supplied, bentonite satisfying the requirements for easy dispersion as well as high quality has been keenly sought.
Efforts have hitherto been made to satisfy the above requirements. For example, a grinding method for minimizing formation of fine particles of 75 μm or smaller which are apt to form lumps was suggested. Removal of fine particles by air classification was also attempted. However, all the conventional attempts failed to achieve satisfactory results.
Bentonite is an alkaline clay mainly comprising a clay mineral montmorillonite and, unlike other clay minerals such as kaolinite or pyrophyllite, has a great cation-exchange capacity of 40 to 120 milliequivalents per 100 g of clay. The exchangeable cations include a sodium ion, a calcium ion, and a magnesium ion. In particular, bentonite having an abundance of sodium ions has such high hydrophilic properties that it absorbs a large quantity of water to increase its own volume remarkably, that is, it exhibits high swellability in water and is finally dispersed to colloidal particles and therefore has been used as a fundamental element of a stabilizing slurry or mud for drilling or boring works. Essential functions required for the material of stabilizing slurries or mud are proper viscosity and water impermeability.
Accordingly, an object of the present invention is to provide readily dispersible bentonite which can be rapidly dispersed in water while minimizing formation of lumps without substantial reduction in viscosity and water impermeability inherent to bentonite.
That is, the present invention relates to readily (water) dispersible bentonite obtained by surface treating bentonite by with adding at least one alkyl-substituted silane compound represented by formula (I);
R.sub.a SiX.sub.b (I)
wherein R represents an alkyl group having 1 to 18 carbon atoms; X represents a methoxy group, an ethoxy group or a halogen atom; a and b each represents 1, 2 or 3, provided that (a+b) is 4; in an amount of not more than 1% by weight based on the bentonite.
Bentonite powder comprises solid bentonite particles with a water content adsorbed on the surface thereof and air filling the gaps among the particles, and the particles agglomerate to form porous clay particles. The clay particles have a highly hydrophilic and highly polar surface and therefore tend to gather. Thus, when bentonite powder is poured into water, the individual bentonite particles do not come into contact with water but gather to form clusters with a large amount of air entrapped therein, and only the outermost part of the clusters is first to be brought into contact with water. Where the bentonite contains abundant sodium ions, the surface of the bentonite cluster absorbs water owing to its strong hydrophilic properties and immediately smells with water to form a continuous water-impermeable gel film. Since the gel film is water impermeable and also adhesive, the air entrapped in the inside of the cluster cannot easily be displaced with outside water. It follows that the bentonite clusters rise to the water surface as lumps in the initial stage of stirring. If the lumps come into contact with each other in a turbulent flow by stirring, they tend to grow into larger lumps. In this stage, the lumps consist of white powder with its inside remaining dry. In the meantime, displacement of inside air with outside water through the gel film proceeds with time, and the water having entered through the gel film swells inside bentonite particles to gradually increase the transparency. At the same time, the lumps are disintegrated from their outermost part and become thinner. Finally, all lumps disappear to provide a uniform dispersion.
Accordingly, in order to accomplish the object of the present invention, it would be an effective means to temporarily suppress formation of a continuous water-impermeable gel film in the initial stage of stirring, namely, when powdered bentonite is poured into water and comes into contact with water. The inventors of the present invention have found that existence of an adequate amount of a hydrophobic substance on the surface of bentonite particles is desirable for that effect. Such a hydrophobic substance as meets the object should satisfy the following conditions; (1) to have no adverse influence on the viscosity and water impermeability of bentonite, (2) to produce a desired effect upon addition of a small amount, (3) to be moderately priced so that the increase in production cost of bentonite may be within an acceptable range, and (4) to be applied to the surface of bentonite particles by a simple and easy method.
The means established by the present inventors is as follows. Coarsely crushed and dried ore of bentonite obtained by a conventional process for bentonite production is pulverized while sprinkling a proper amount of at least one of the following alkyl-substituted silane compounds, or powdered bentonite is mixed with a proper amount of at least one of the alkyl-substituted silane compounds which is added through sprinkling over the powdered bentonite, the compound thereby adhering as a hydrophobic substance on the surface of bentonite particles.
The alkyl-substituted silane compounds which can be used in the present invention are represented by formula (I):
R.sub.a SiX.sub.b (I)
wherein R represents an alkyl group having 1 to 18 carbon atoms (more preferably 1 to 6 carbon atoms); X represents a methoxy group, an ethoxy group or a halogen atom; a and b each represent 1, 2 or 3; and (a+b) is 4.
Typical examples of the alkyl-substituted silane compounds include methyltrimethoxysilane [CH3 Si(OCH3)3 ], trimethylchlorosilane [(CH3)3 SiCl], trimethylmethoxysilane [(CH3)3 SiOCH3 ], hexyltrimethoxysilane [C6 H13 Si(OCH3)3 ], dodecyltriethoxysilane [(CH12 H25 Si(OC2 H5)3 ], and octadecyltriethoxysilane [C18 H37 Si(OC2 H5)3 ].
There is generally an optimum range of the amount of the alkyl-substituted silane compound to be added to bentonite depending on the kind of bentonite and the kind of the alkyl-substituted silane compound. If the amount of the alkyl-substituted silane compound added is lower than the respective optimum range, inhibition of the formation of lumps is insufficient. If the amount exceeds the optimum range, although the formation of lumps is inhibited, the bentonite clusters exhibit water repellency and thereby poor dispersibility. The optimum range for a combination of specific bentonite species and a specific alkyl-substituted silane compound can be decided by preliminary experimentation for evaluating the inhibitory effect on lump formation as well as the viscosity and water impermeability of the resulting dispersion. In many cases, the amount to be added for producing a noticeable effect is from 0 to 1% by weight, preferably from 0.05 to 0.5% by weight, based on bentonite.
The water content of the bentonite to which the alkyl-substituted silane compound is added may be in the same range as that of commonly available bentonite products, i.e., in the range of from about 6 to 10% by weight. There is no need to dry or dehydrate bentonite to a substantially water-free state as has been necessary in a conventional surface treatment of inorganic silicate fillers with a silane coupling agent. Neither is it necessary to limit the water content of bentonite to be treated.
The alkyl-substituted silane compound added to bentonite powder in an amount of not more than 1% by weight renders a part of the surface of bentonite particles hydrophobic owing to its remarkable water-repelling action attributed to the alkylsilyl group thereof. As a result, when the thus treated bentonite is poured into water, the surface of the bentonite particles is moderately prevented from absorbing water to form a continuous water-impermeable gel film. It follows that the clusters of bentonite particles achieve rapid displacement of the internal air with the outside water while minimizing formation and growth of lumps, and the clusters are crumbled and dispersed in water at a considerably increased speed by the turbulent flow of stirring.
The alkyl-substituted silane compound used in the present invention is hydrolyzed on contact with water, thereby releasing the methoxy or ethoxy group by dealcoholization, or halogen atom by dehalogenation and, at the same time, providing a hydroxyl group on the silicon atom (to form a silanol group). Since the resulting silanol group is hydrophilic, it is adhered to the hydrophilic surface of the water-containing bentonite particles.
As a technique relevant to the present invention, U.S. Pat. No. 5,292,908 discloses modified bentonite which is dispersed in water to perform a function of adjusting rheology of an aqueous fluid, which is obtained by adding an alkyltrialkoxysilane to bentonite in such an amount that the resulting bentonite may not lose the water dispersibility, usually in an amount of 1 to 10 parts by weight per 100 parts by weight of bentonite, followed by treating in a water-free atmosphere to add an alkylsilico group to a part of the surface of bentonite particles. This technique is quite different from the present invention; the modified bentonite of U.S. Pat. No. 5,292,908 has an alkylsilico group permanently added to the surface thereof through a covalent bond that is formed by condensation (dealcoholation) between a hydroxyl group on the edge of montmorillonite crystal grains and the alkyltrialkoxysilane. Therefore, the treatment is accomplished under a water-free condition. On the other hand, in the present invention, the alkyl-substituted silane compound merely has to be physically adhered to the surface of water-containing bentonite particles so that the surface of the bentonite particles may temporarily exhibit hydrophobic properties to prevent formation of lumps immediately after the bentonite particles are poured into water and in the initial stage of stirring. Therefore, the silane compound does not need to be permanently bound to the surface of bentonite particles through a chemical bond, and the amount of the silane compound to be added may be lower than the lower limit required for the above-described modified bentonite. The viscosity and water impermeability inherently possessed by bentonite are substantially guaranteed in the presence of such an alkyl-substituted silane compound.
The present invention will now be illustrated in greater detail with reference to examples and comparative examples, but it should be understood that the present invention is not construed as being limited thereto. Unless otherwise indicated, all the parts and percents are by weight.
Coarsely crushed and dried bentonite ore from Greybull, Wyo., U.S.A., weighing 25 kg (water content: 9.0%) was uniformly spread on a polyethylene sheet to a thickness of about 10 mm, and 50 g of methyltrimethoxysilane was sprayed over the bentonite. Immediately thereafter, the bentonite ore was gathered at the central portion of the sheet and passed through a hammer mill twice to obtain pulverized powder of treated bentonite (hereinafter designated Treated Bentonite I). For comparison, non-treated bentonite pulverized powders were prepared in the same manner as described above except for using no methyltrimethoxysilane. The particle size distribution of the pulverized powders measured through a dry sieve test is shown in Table 1. As shown in Table 1, both the Treated Bentonite I and the non-treated bentonite had approximately the same particle size distribution.
TABLE 1
______________________________________
Particle Size Distribution
Non-treated
Treated
Sieve Opening Bentonite Bentonite I
(μm) (%) (%)
______________________________________
150 or more 2.4 3.9
150-75 20.0 15.3
75-45 34.6 32.8
45 or less 43.0 48.0
______________________________________
Treated Bentonite I was compared with the non-treated bentonite in inhibitory effect on lump formation as follows.
In a 1 l-beaker was put 600 ml of tap water (conductivity: 133 μS/cm; pH 7.2). Sample bentonite (42 g) was added thereto and immediately thereafter stirred in a DC 6-wing turbine stirrer "Model DS-2R" at 500 rpm for 5minutes. The stirring was stopped to observe lumps of powder rising to the water surface. The results obtained are shown in Table 2. It is seen that Treated Bentonite I according to the present invention extremely suppresses formation of lumps, and the lumps allow rapid permeation of water.
TABLE 2
______________________________________
Non-treated
Treated
Bentonite
Bentonite I
______________________________________
Size of lumps 2-5 1-2
(diameter; mm)
Number of lumps 40 10
State of lumps dry powder the inside
(as visually remaining in
permeated
observed) the inside with water
______________________________________
After the observation, the stirring was resumed. The lumps of Treated Bentonite I completely disappeared after 10 minutes (in total) of stirring. On the other hand, it took 30 minutes (in total) of stirring for the lumps of the non-treated bentonite to completely disappear. The viscosity and water impermeability of each of the resulting bentonite dispersion are shown in Table 3. The viscosity was measured with a Fan VG rotational viscometer which is in conformity with the specification of the U.S. Petroleum Institute. The water impermeability was evaluated in terms of fluid loss (expressed in amount of filtrate obtained in 30 minutes under pressure of 3 kgf/cm2 and thickness of filter cake) as measured with a constant pressure filtration tester according to the same specification.
TABLE 3
______________________________________
Non-treated
Treated
Bentonite
Bentonite I
______________________________________
Viscosity:
Apparent viscosity (cP)
13.4 15.5
Plastic viscosity (cP)
10.6 12.3
Yield value (lb/100 ft.sup.2)
5.6 6.4
Gel strength (lb/100 ft.sup.2)
Initial 1.5 1.5
After 10 minutes 7.5 6.5
Water impermeability:
Fluid loss 14.2 13.2
(ml/30 min, 3 kgf · cm.sup.-2)
Thickness of cake (mm)
1.8 1.6
______________________________________
As is apparent from the results of Table 3, Treated Bentonite I was proved equal or even superior to the non-treated bentonite in the viscosity and water impermeability.
Bentonite was treated with various alkyl-substituted silane compounds shown in Table 4 in the same manner as in Example 1 to prepare Treated Bentonite II to VI. Treated bentonite II to VI were evaluated by a dispersion test in the same manner as in Example 1. The results obtained are shown in Table 4. It is seen that the treated bentonite according to the present invention exhibits excellent dispersibility while retaining viscosity and water impermeability.
TABLE 4
__________________________________________________________________________
Non-treated
Bentonite
II III IV V VI
__________________________________________________________________________
Treating agent
none 0.3% 0.3% 0.2% 0.3% 0.3%
trimethyl-
trimethyl-
hexyltri-
dodecyl-
octadecyl-
chloro-
methoxy-
methoxy-
triethoxy-
triethoxy-
silane
silane
silane
silane
silane
Time required for lumps
33 15 13 15 13 16
to disappear (min)
Viscosity:
Apparent viscosity (cP)
12.5 13.9 12.4 13.5 13.5 14.8
Plastic viscosity (cP)
10.5 10.3 10.8 9.0 11.0 12.7
Yield value (lb/100 ft.sup.2)
4.0 7.2 3.2 9.0 5.0 4.1
Gel strength (lb/100 ft.sup.2):
Initial 1.5 1.5 1.5 1.0 1.5 1.0
After 10 minutes
6.5 8.0 8.0 6.0 8.0 5.5
Water impermeability:
Fluid loss 16.3 14.1 14.8 15.8 15.2 13.5
(ml/30 min, 3 kgf · cm.sup.-2)
Thickness of cake (mm)
2.0 1.9 2.1 2.0 2.0 1.8
__________________________________________________________________________
In an Eirich mixer "Model RV02" was charged 3000 g of bentonite "Superclay" (a product of Hojun Yoko K.K., produced by grinding bentonite of Greybull, Wyo., U.S.A., in a roller mill), and a varied amount of methyltrimethoxysilane was added thereto as shown in Table 5, followed by stirring at 900 rpm for 5 minutes. The dispersibility of the resulting treated bentonite was evaluated by observing the state of lumps after 5 minutes of stirring in water in the same manner as in Example 1. The results obtained are shown in Table 5.
TABLE 5
______________________________________
Sample No. SC-0 SC-1 SC-2 SC-3 SC-4 SC-5
______________________________________
Composition (part):
Superclay 100 100 100 100 100 100
Methyltri- 0 0.05 0.1 0.2 0.5 1.0
methoxysilane
Dispersibility
(5 minutes' stirring):
Size of lumps
6-3 3-2 2-1 2-1 2-1 1-0
(diameter, mm)
Number of lumps
50 30 20 20 20 10
or more
State of lumps
D D W W W W
______________________________________
Note
D: Dry powder remained in the inside of lumps.
W: Wet as a whole (with water permeated to the inside).
As is apparent from the results in Table 5, addition of 0.05% methyltrimethoxysilane (SC-1) appreciably reduces lump formation as compared with the untreated bentonite (SC-0), and lump formation is further suppressed by addition of increased amounts, i.e., 0.1% or more, of methyltrimethoxysilane to exhibit satisfactory water dispersibility.
Performance of samples SC-0, SC-2, and SC-3 as mud was tested in accordance with the bentonite testing method specified by the U.S. Petroleum Institute. The results obtained are shown in Table 6. As is apparent from the results of Table 6, the treated bentonite according to the present invention was satisfactory in viscosity and water impermeability.
TABLE 6
______________________________________
SC-0 SC-2 SC-3
After After After
Initial
1 Night Initial 1 Night
Initial
1 Night
______________________________________
Apparent 20.0 21.6 19.2 21.2 19.8 21.6
Viscosity (cP)
Plastic 15.1 16.3 14.2 16.3 15.1 16.2
viscosity (cP)
Yield value
9.7 10.5 10.0 9.8 9.3 10.8
(lb/100 ft.sup.2)
Gel strength
(lb/100 ft.sup.2)
Initial 1.5 1.0 1.5 1.5 1.0 1.0
After 10 4.0 4.5 5.0 7.0 6.0 7.0
minutes
Fluid loss
12.0 11.4 12.0 11.3 11.9 11.2
(ml/30 min,
3 kgf · cm.sup.-2)
Thickness of
2.0 1.9 2.2 2.0 2.2 2.1
cake (mm)
______________________________________
As having been fully described and demonstrated, the present invention brings about the following effects.
When the bentonite particles having adhered on the surface thereof an alkyl-substituted silane compound are poured into water and stirred in the preparation of an aqueous bentonite dispersion, the strong water repellency of the alkylsilyl group prevents clusters of the bentonite particles from absorbing water at the outermost part thereof and from forming a continuous water impermeable gel film there in the initial stage of stirring. As a result, formation and growth of lumps of powder are suppressed and, at the same time, displacement of air entrapped inside the cluster with the outside water rapidly proceeds, whereby the whole cluster is swollen with water. The small lumps of powder having lost buoyancy are sufficiently moved in water by a stirring turbulent flow and rapidly become thinner and uniformly dispersed. The readily dispersible bentonite according to the present invention retains the viscosity and water impermeability essential to bentonite and therefore makes it possible to remarkably reduce the time and energy for dispersing bentonite in the preparation of a soil stabilizing slurry or mud for use in ground drilling works.
While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Claims (2)
1. Readily dispersible bentonite obtained by surface-treating bentonite with at least one alkyl-substituted silane compound represented by formula (I):
R.sub.a SiX.sub.b (I)
wherein R represents an alkyl group having 1 to 18 carbon atoms; X represents a methoxy group, an ethoxy group or a halogen atom; a and b each represents 1, 2 or 3, provided that (a+b) is 4;
in an amount of not more than 1% by weight based on the bentonite.
2. Readily dispersible bentonite as claimed in claim 1, wherein said alkyl-substituted silane compound is selected from the group consisting of methyltrimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, hexyltrimethoxysilane, dodecyltriethoxysilane, and octadecyltriethoxysilane.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7034692A JPH08208218A (en) | 1995-02-01 | 1995-02-01 | Easily dispersible bentonite |
| JP7-34692 | 1995-02-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US5491248A true US5491248A (en) | 1996-02-13 |
Family
ID=12421438
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US08/425,534 Expired - Fee Related US5491248A (en) | 1995-02-01 | 1995-04-20 | Readily dispersible bentonite |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5491248A (en) |
| JP (1) | JPH08208218A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU733785B2 (en) * | 1996-05-08 | 2001-05-24 | Robert John Milland | Method and apparatus for decoding a video signal |
| US20130206235A1 (en) * | 2010-10-29 | 2013-08-15 | The Yokohama Rubber Co., Ltd. | Electrolyte for photoelectric conversion element, and photoelectric conversion element and dye-sensitized solar cell using same |
| US20140026785A1 (en) * | 2012-07-26 | 2014-01-30 | Dolly Nicholas | Synthetic modifier for hot asphaltic mixes for road paving and method of making same |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008290923A (en) * | 2007-05-28 | 2008-12-04 | Kurosaki Hakudo Kogyo Kk | Modified bentonite with improved water dispersibility and its manufacturing method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4528038A (en) * | 1984-06-28 | 1985-07-09 | General Electric Company | Organoaluminosiloxane coating compositions and coated substrate |
| US5110501A (en) * | 1980-10-03 | 1992-05-05 | Southern Clay Products, Inc. | Process for manufacturing organoclays having enhanced gelling properties |
| US5292908A (en) * | 1992-03-09 | 1994-03-08 | Hojun Kogyo Co., Ltd. | Modified bentonite |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02247918A (en) * | 1989-03-22 | 1990-10-03 | Matsushita Electric Ind Co Ltd | Manufacture of back-lighted operation key top |
-
1995
- 1995-02-01 JP JP7034692A patent/JPH08208218A/en active Pending
- 1995-04-20 US US08/425,534 patent/US5491248A/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5110501A (en) * | 1980-10-03 | 1992-05-05 | Southern Clay Products, Inc. | Process for manufacturing organoclays having enhanced gelling properties |
| US4528038A (en) * | 1984-06-28 | 1985-07-09 | General Electric Company | Organoaluminosiloxane coating compositions and coated substrate |
| US5292908A (en) * | 1992-03-09 | 1994-03-08 | Hojun Kogyo Co., Ltd. | Modified bentonite |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU733785B2 (en) * | 1996-05-08 | 2001-05-24 | Robert John Milland | Method and apparatus for decoding a video signal |
| US20130206235A1 (en) * | 2010-10-29 | 2013-08-15 | The Yokohama Rubber Co., Ltd. | Electrolyte for photoelectric conversion element, and photoelectric conversion element and dye-sensitized solar cell using same |
| US8957305B2 (en) * | 2010-10-29 | 2015-02-17 | The Yokohama Rubber Co., Ltd. | Electrolyte for photoelectric conversion element, and photoelectric conversion element and dye-sensitized solar cell using same |
| US20140026785A1 (en) * | 2012-07-26 | 2014-01-30 | Dolly Nicholas | Synthetic modifier for hot asphaltic mixes for road paving and method of making same |
| US8852332B2 (en) * | 2012-07-26 | 2014-10-07 | Js3D Technology Company Limited | Synthetic modifier for hot asphaltic mixes for road paving and method of making same |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08208218A (en) | 1996-08-13 |
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